Ad-hoc directional communication in contention access period

ABSTRACT

Certain aspects of the present disclosure relate to a method for efficient ad-hoc peer to peer communication in a contention access period, while antenna directions of communicating peers can point to each other. Certain aspects of the present disclosure relate to a method for improved association of a device in a wireless network with a controller of the network.

CLAIM OF PRIORITY UNDER 35 U.S.C. §119

The present Application for Patent claims benefit of U.S. provisionalapplication Ser. No. 61/169,534 filed Apr. 15, 2009, and U.S.provisional application Ser. No. 61/177,411 filed May 12, 2009, andassigned to the assignee hereof and are hereby expressly incorporated byreference herein.

BACKGROUND

1. Field

Certain aspects of the present disclosure generally relate to a wirelesscommunication and, more particularly, to association betweencommunicating devices and to ad-hoc directional communication in acontention access period.

2. Background

In emerging wireless communication standards, such as the Institute ofElectrical and Electronics Engineers (IEEE) 802.15.3c standard, anetwork coordinator scheduling (e.g., control by a piconet controller oran access point) is mandatory to access a medium for anydevice-to-device communication. However, efficiency of this access canbe very low, particularly for data applications with very random andbursty traffic.

A channel time allocation (CTA), which is a time division multiplexing(TDM) based approach, can provide means to support streamingapplications with high data rates. On the other hand, the use of largeamount of bursty data is not well supported in the IEEE 802.15.3cstandard.

The link budget for transmitting high data rates over 60 GHz frequencyband supported by standards such as the IEEE 802.15.3c, IEEE 802.11adand European Computer Manufacturer's Association Technical Committee 48(ECMA-TC48) requires considerable antenna gain as well as flexibility inthe orientation of end-point devices. This directional communicationpresents a new challenge for devices communicating with multiple peersin multiple directions. Such devices need to be informed in advance towhich direction to set their antennas. However, the nature ofcontention-based traffic is that it is not always possible to know inadvance which directions to use, since anyone of the potential peers maygain access to a medium. Several attempts and restrictions were appliedin a contention access period (CAP) specified by the IEEE 802.15.3cstandard, but none of them provided an efficient solution for thisproblem.

Therefore, there is a need in the art for a method to provide efficientad-hoc peer-to-peer communication in the CAP while ensuring that antennadirections of communicating peers point to each other. Preceding this,it is desirable that peers (i.e., wireless nodes of the network) areassociated with the network coordinator.

SUMMARY

Certain aspects provide a method for wireless communications. The methodgenerally includes monitoring, by an apparatus, a medium in a contentionaccess period (CAP) for availability of the medium for data transmissionby the apparatus, after determining the medium is available for datatransmission by the apparatus, obtaining the medium by transmitting,from the apparatus, a common mode signaling (CMS) frame in the CAP, andtransmitting, from the apparatus, at least one data frame to anotherapparatus in the CAP over a wireless channel of the medium afterobtaining the medium.

Certain aspects provide an apparatus for wireless communications. Theapparatus generally includes a monitoring circuit configured to monitora medium in a contention access period (CAP) for availability of themedium for data transmission by the apparatus, and a transmitterconfigured to obtain the medium by transmitting a common mode signaling(CMS) frame in the CAP, after determining the medium is available fordata transmission by the apparatus, and wherein the transmitter is alsoconfigured to transmit at least one data frame to another apparatus inthe CAP over a wireless channel of the medium after obtaining themedium.

Certain aspects provide an apparatus for wireless communications. Theapparatus generally includes means for monitoring a medium in acontention access period (CAP) for availability of the medium for datatransmission by the apparatus, means for obtaining the medium bytransmitting, from the apparatus, a common mode signaling (CMS) frame inthe CAP, after determining the medium is available for data transmissionby the apparatus, and means for transmitting at least one data frame toanother apparatus in the CAP over a wireless channel of the medium afterobtaining the medium.

Certain aspects provide a computer-program product for wirelesscommunications. The computer-program product includes acomputer-readable medium encoded with instructions executable tomonitor, by an apparatus, a medium in a contention access period (CAP)for availability of the medium for data transmission by the apparatus,obtain the medium by transmitting, from the apparatus, a common modesignaling (CMS) frame in the CAP, after determining the medium isavailable for data transmission by the apparatus, and transmit, from theapparatus, at least one data frame to another apparatus in the CAP overa wireless channel of the medium after obtaining the medium.

Certain aspects provide a wireless node. The wireless node generallyincludes at least one antenna, a monitoring circuit configured tomonitor a medium in a contention access period (CAP) for availability ofthe medium for data transmission by the wireless node, and a transmitterconfigured to obtain the medium by transmitting via the at least oneantenna a common mode signaling (CMS) frame in the CAP, afterdetermining the medium is available for data transmission by thewireless node, and wherein the transmitter is also configured totransmit via the at least one antenna at least one data frame to anotherwireless node in the CAP over a wireless channel of the medium afterobtaining the medium.

Certain aspects provide a method for wireless communications. The methodgenerally includes receiving, by an apparatus, a common mode signaling(CMS) frame transmitted by another apparatus indicating access to amedium for data communication by the other apparatus in a contentionaccess period (CAP), receiving, from the other apparatus once the accessto the medium for data communication is indicated at the apparatus, atleast one data frame over a wireless channel of the medium in the CAP,and transmitting, to the other apparatus, an acknowledgement that the atleast one data frame is successfully received over the wireless channelof the medium in the CAP.

Certain aspects provide an apparatus for wireless communications. Theapparatus generally includes a receiver configured to receive a commonmode signaling (CMS) frame transmitted by another apparatus indicatingaccess to a medium for data communication by the other apparatus in acontention access period (CAP), wherein the receiver is also configuredto receive, from the other apparatus once the access to the medium fordata communication is indicated at the apparatus, at least one dataframe over a wireless channel of the medium in the CAP, and atransmitter configured to transmit, to the other apparatus, anacknowledgement that the at least one data frame is successfullyreceived over the wireless channel of the medium in the CAP.

Certain aspects provide an apparatus for wireless communications. Theapparatus generally includes means for receiving a common mode signaling(CMS) frame transmitted by another apparatus indicating access to amedium for data communication by the other apparatus in a contentionaccess period (CAP), means for receiving, from the other apparatus oncethe access to the medium for data communication is indicated at theapparatus, at least one data frame over a wireless channel of the mediumin the CAP, and means for transmitting, to the other apparatus, anacknowledgement that the at least one data frame is successfullyreceived over the wireless channel of the medium in the CAP.

Certain aspects provide a computer-program product for wirelesscommunications. The computer-program product includes acomputer-readable medium encoded with instructions executable toreceive, by an apparatus, a common mode signaling (CMS) frametransmitted by another apparatus indicating access to a medium for datacommunication by the other apparatus in a contention access period(CAP), receive, from the other apparatus once the access to the mediumfor data communication is indicated at the apparatus, at least one dataframe over a wireless channel of the medium in the CAP, and transmit, tothe other apparatus, an acknowledgement that the at least one data frameis successfully received over the wireless channel of the medium in theCAP.

Certain aspects provide a wireless node. The wireless node generallyincludes at least one antenna, a receiver configured to receive via theat least one antenna a common mode signaling (CMS) frame transmitted byanother wireless node indicating access to a medium for datacommunication by the other wireless node in a contention access period(CAP), wherein the receiver is also configured to receive via the atleast one antenna, from the other wireless node once the access to themedium for data communication is indicated at the wireless node, atleast one data frame over a wireless channel of the medium in the CAP,and a transmitter configured to transmit via the at least one antenna,to the other wireless node, an acknowledgement that the at least onedata frame is successfully received over the wireless channel of themedium in the CAP.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description,briefly summarized above, may be had by reference to aspects, some ofwhich are illustrated in the appended drawings. It is to be noted,however, that the appended drawings illustrate only certain typicalaspects of this disclosure and are therefore not to be consideredlimiting of its scope, for the description may admit to other equallyeffective aspects.

FIG. 1 illustrates an example wireless communication system inaccordance with certain aspects of the present disclosure.

FIG. 2 illustrates various components that may be utilized in a wirelessdevice in accordance with certain aspects of the present disclosure.

FIG. 3 illustrates an example transmitter that may be used within awireless communication system in accordance with certain aspects of thepresent disclosure.

FIG. 4 illustrates an example receiver that may be used within awireless communication system in accordance with certain aspects of thepresent disclosure.

FIG. 5 illustrates an association procedure in accordance with certainaspects of the present disclosure.

FIG. 6 illustrates example operations for associating a device with apiconet controller in accordance with certain aspects of the presentdisclosure.

FIG. 6A illustrates example components capable of performing theoperations illustrated in FIG. 6.

FIG. 7 illustrates an example of association flow in accordance withcertain aspects of the present disclosure.

FIG. 8 illustrates another example of association flow in accordancewith certain aspects of the present disclosure.

FIG. 9 illustrates example operations for ad-hoc directionaltransmission in a contention access period (CAP) in accordance withcertain aspects of the present disclosure.

FIG. 9A illustrates example components capable of performing theoperations illustrated in FIG. 9.

FIG. 10 illustrates an example scenario for ad-hoc directionaltransmission in the CAP with no antenna-pattern training in accordancewith certain aspects of the present disclosure.

FIG. 11 illustrates example operations for antenna-pattern training as apart of the ad-hoc directional transmission illustrated in FIG. 9 inaccordance with certain aspects of the present disclosure.

FIG. 11A illustrates example components capable of performing theoperations illustrated in FIG. 11.

FIG. 12 illustrates an example scenario for ad-hoc directionaltransmission in the CAP with antenna-pattern training in accordance withcertain aspects of the present disclosure.

FIG. 13 illustrates an example of an empty common mode signaling (CMS)frame in accordance with certain aspects of the present disclosure.

FIG. 14 illustrates a structure of a physical layer (PHY) header of theCMS frame in accordance with certain aspects of the present disclosure.

FIG. 15 illustrates a structure of a medium access control (MAC) headerof the CMS frame in accordance with certain aspects of the presentdisclosure.

FIG. 16 illustrates a structure of a fragmentation control field of theMAC header in accordance with certain aspects of the present disclosure.

FIG. 17 illustrates a structure of a Duration Information Element (IE)field of the CMS command frame in accordance with certain aspects of thepresent disclosure.

FIG. 18 illustrates an example of busy medium durations in the case ofad-hoc directional transmission without training of antenna patterns inaccordance with certain aspects of the present disclosure.

FIG. 19 illustrates an example of busy medium durations in the case ofad-hoc directional transmission with training of antenna patterns inaccordance with certain aspects of the present disclosure.

FIG. 20 illustrates an example of quasi-omni preamble reception inaccordance with certain aspects of the present disclosure.

FIG. 21 illustrates a frame structure with long preamble for accessingthe medium in the CAP in accordance with certain aspects of the presentdisclosure.

DETAILED DESCRIPTION

Various aspects of the disclosure are described more fully hereinafterwith reference to the accompanying drawings. This disclosure may,however, be embodied in many different forms and should not be construedas limited to any specific structure or function presented throughoutthis disclosure. Rather, these aspects are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of the disclosure to those skilled in the art. Based on theteachings herein one skilled in the art should appreciate that the scopeof the disclosure is intended to cover any aspect of the disclosuredisclosed herein, whether implemented independently of or combined withany other aspect of the disclosure. For example, an apparatus may beimplemented or a method may be practiced using any number of the aspectsset forth herein. In addition, the scope of the disclosure is intendedto cover such an apparatus or method which is practiced using otherstructure, functionality, or structure and functionality in addition toor other than the various aspects of the disclosure set forth herein. Itshould be understood that any aspect of the disclosure disclosed hereinmay be embodied by one or more elements of a claim.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any aspect described herein as “exemplary”is not necessarily to be construed as preferred or advantageous overother aspects.

In the following detailed description, various aspects of the disclosuremay be described in the context of a wireless network or “piconet” inaccordance to the IEEE 802.15 family of standards (whether adopted orproposed). While these disclosed aspects may be well suited for use withsuch networks in which an access point (AP) may serve as a piconetcoordinator (PNC), those skilled in the art will readily appreciate thatthese disclosed aspects are likewise applicable for use in various othercommunication environments utilizing any type of access points (APs) andaccess terminals (ATs), including, but not limited to, networks inaccordance with the IEEE 802.11 family of standards and may, in fact,allow networks in accordance with different standards to betterco-exist. Accordingly, any reference to an IEEE 802.15 compliant networkis intended only to illustrate the disclosed aspects, with theunderstanding that such disclosed aspects have a wide range ofapplications.

The teachings herein may be incorporated into (e.g., implemented withinor performed by) a variety of wired or wireless apparatuses (e.g.,nodes). In some aspects, a wireless node implemented in accordance withthe teachings herein may comprise an access point or an access terminal.

An access point (“AP”) may comprise, be implemented as, or known asNodeB, Radio Network Controller (“RNC”), eNodeB, Base Station Controller(“BSC”), Base Transceiver Station (“BTS”), Base Station (“BS”),Transceiver Function (“TF”), Radio Router, Radio Transceiver, BasicService Set (“BSS”), Extended Service Set (“ESS”), Radio Base Station(“RBS”), or some other terminology.

An access terminal (“AT”) may comprise, be implemented as, or known asan access terminal, a subscriber station, a subscriber unit, a mobilestation, a remote station, a remote terminal, a user terminal, a useragent, a user device, user equipment, or some other terminology. In someimplementations, an access terminal may comprise a cellular telephone, acordless telephone, a Session Initiation Protocol (“SIP”) phone, awireless local loop (“WLL”) station, a personal digital assistant(“PDA”), a handheld device having wireless connection capability, orsome other suitable processing device connected to a wireless modem.Accordingly, one or more aspects taught herein may be incorporated intoa phone (e.g., a cellular phone or smart phone), a computer (e.g., alaptop), a portable communication device, a portable computing device(e.g., a personal data assistant), an entertainment device (e.g., amusic or video device, or a satellite radio), a global positioningsystem device, or any other suitable device that is configured tocommunicate via a wireless or wired medium.

In some aspects, the node is a wireless node. Such wireless nodes mayprovide, for example, connectivity for or to a network (e.g., a personalarea network or piconet, wide area network such as the Internet, or acellular network) via a wired or wireless communication link.

Although particular aspects are described herein, many variations andpermutations of these aspects fall within the scope the disclosure.Although some benefits and advantages of the preferred aspects arementioned, the scope of the disclosure is not intended to be limited toparticular benefits, uses, or objectives. Rather, aspects of thedisclosure are intended to be broadly applicable to different wirelesstechnologies, system configurations, networks, and transmissionprotocols, some of which are illustrated by way of example in thefigures and in the following description of the preferred aspects. Thedetailed description and drawings are merely illustrative of thedisclosure rather than limiting, the scope of the disclosure beingdefined by the appended claims and equivalents thereof.

An Example Wireless Communication System

FIG. 1 illustrates an example of a wireless communication system 100(i.e., a Piconet 1) in which aspects of the present disclosure may beemployed. As illustrated, Piconet 1 may include a number of wirelessdevices 102 or “terminals” 1A-1E that can communicate with one anotherusing relatively short-range wireless links 104. In the illustratedexample, terminal 1E acts as a PNC for Piconet 1. Although illustratedwith five devices, it should be appreciated that any number of devices(i.e., two or more) may form a wireless personal area network.

Each of the terminals 102 in the Piconet 1 may include, among otherthings, a wireless transceiver to support wireless communication andcontroller functionality to manage communication with the network. Thecontroller functionality may be implemented within one or more digitalprocessing devices. The wireless transceiver may be coupled to one ormore antennas to facilitate the transmission of signals into and thereception of signals from a wireless channel. Any type of antennas maybe used including, for example, dipoles, patches, helical antennas,antenna arrays, and/or others.

The devices in the Piconet 1 may include any of a wide variety ofdifferent device types including, for example, laptop, desktop, palmtop,or tablet computers having wireless networking functionality, computerperipherals having wireless networking capability, personal digitalassistants (PDAs) having wireless networking capability, cellulartelephones and other handheld wireless communicators, pagers, wirelessnetwork interface modules (e.g., wireless network interface cards, etc.)incorporated into larger systems, multimedia devices having wirelessnetworking capability, audio/visual devices having wireless networkingcapability, home appliances having wireless networking capability,jewelry or other wearable items having wireless networking capability,wireless universal serial bus (USB) devices, wireless digital imagingdevices (e.g., digital cameras, camcorders, etc.), wireless printers,wireless home entertainment systems (e.g., DVD/CD players, televisions,MP3 players, audio devices, etc.), and/or others. In one configuration,for example, a wireless personal area network may include a user'slaptop computer that is wirelessly communicating with the user'spersonal digital assistant (PDA) and the user's printer in a short-rangenetwork. In another possible configuration, a wireless personal areanetwork may be formed between various audio/visual devices in, forexample, a user's living room. In yet another configuration, a user'slaptop computer may communicate with terminals associated with otherusers in a vicinity of the user. Many other scenarios are also possible.

Standards have been developed, and are currently in development, toprovide a framework to support development of interoperable productsthat are capable of operating as part of a wireless personal areanetwork (e.g., the Bluetooth standard (Specification of the BluetoothSystem, Version 1.2, Bluetooth SIG, Inc., November 2003), the IEEE802.15 standards, etc.). The IEEE 802.15.3c standard, for example, is ahigh data rate wireless personal area network standard. In accordancewith the IEEE 802.15.3c standard, one of the terminals within a piconetis selected as a Piconet Coordinator (PNC) to coordinate the operationof the network. For example, with reference to FIG. 1, the device PNC 1Erepresents a PNC for the Piconet 1 in an IEEE 802.15.3c implementation.

As illustrated, PNC 1E may transmit a beacon signal 110 (or simply“beacon”) to other devices of Piconet 1, which may help the otherterminals within Piconet 1 synchronize their timing with PNC 1E. Thus,the beacon, typically sent at the beginning of every super-frame,contains information that may be used to time-synchronize the terminalsin the piconet. Each terminal in the piconet, including the PNC, mayreset its super-frame clock to zero at the beginning of the beaconpreamble. If a terminal does not hear a beacon, it may reset itssuper-frame clock to zero at the instant where it expected to hear thebeginning of the beacon preamble (e.g., based on previous super-frametiming).

FIG. 2 illustrates various components that may be utilized in a wirelessdevice 202 that may be employed within the wireless communication system100. The wireless device 202 is an example of a device that may beconfigured to implement the various methods described herein. Thewireless device 202 may be the PNC 1E or a terminal 102 in the Piconet1.

The wireless device 202 may include a processor 204 which controlsoperation of the wireless device 202. The processor 204 may also bereferred to as a central processing unit (CPU). Memory 206, which mayinclude both read-only memory (ROM) and random access memory (RAM),provides instructions and data to the processor 204. A portion of thememory 206 may also include non-volatile random access memory (NVRAM).The processor 204 typically performs logical and arithmetic operationsbased on program instructions stored within the memory 206. Theinstructions in the memory 206 may be executable to implement themethods described herein.

The wireless device 202 may also include a housing 208 that may includea transmitter 210 and a receiver 212 to allow transmission and receptionof data between the wireless device 202 and a remote location. Thetransmitter 210 and receiver 212 may be combined into a transceiver 214.An antenna 216 may be attached to the housing 208 and electricallycoupled to the transceiver 214. The wireless device 202 may also include(not shown) multiple transmitters, multiple receivers, multipletransceivers, and/or multiple antennas.

The wireless device 202 may also include a signal detector 218 that maybe used in an effort to detect and quantify the level of signalsreceived by the transceiver 214. The signal detector 218 may detect suchsignals as total energy, energy per subcarrier per symbol, powerspectral density and other signals. The wireless device 202 may alsoinclude a digital signal processor (DSP) 220 for use in processingsignals.

The various components of the wireless device 202 may be coupledtogether by a bus system 222, which may include a power bus, a controlsignal bus, and a status signal bus in addition to a data bus.

FIG. 3 illustrates an example of a transmitter 302 that may be usedwithin a wireless communication system 100 that utilizes single-carrieror some other transmission technique. Portions of the transmitter 302may be implemented in the transmitter 210 of a wireless device 202. Thetransmitter 302 may be implemented in the PNC 1E for transmitting data304 to a terminal 102. The transmitter 302 may also be implemented in aterminal 102 for transmitting data 304 to the PNC 1E.

Data 304 to be transmitted are shown being provided as input to a mapper306. The mapper 306 may map the data stream 304 onto constellationpoints. The mapping may be done using some modulation constellation,such as binary phase-shift keying (BPSK), quadrature phase-shift keying(QPSK), 8 phase-shift keying (8PSK), quadrature amplitude modulation(QAM), etc. Thus, the mapper 306 may output a symbol stream 308, whichmay represents an input into a preamble insertion unit 310.

The preamble insertion unit 310 may be configured for inserting apreamble sequence at the beginning of the input symbol stream 308, andgenerates a corresponding data stream 312. The preamble may be known atthe receiver and may be utilized for time and frequency synchronization,channel estimation, equalization and channel decoding. The output 312 ofthe preamble insertion unit 310 may then be up-converted to a desiredtransmit frequency band by a radio frequency (RF) front end 314. Anantenna 316 may then transmit a resulting signal 318 over a wirelesschannel.

FIG. 4 illustrates an example of a receiver 402 that may be used withina wireless device 202 that utilizes a single-carrier or some othertransmission technique. Portions of the receiver 402 may be implementedin the receiver 212 of a wireless device 202. The receiver 402 may beimplemented in a terminal 102 for receiving data 404 from the PNC 1E.The receiver 402 may also be implemented in the PNC 1E for receivingdata 404 from a terminal 102.

When a signal 404 is received by an antenna 406, it may bedown-converted to a baseband signal 410 by an RF front end 408. A frameformat of the received signal for single-carrier data communicationstypically comprises a preamble followed by a data portion. A portion ofthe preamble 412 may be used for channel estimation by unit 416.Received data 414 may be processed by an equalization unit 420 employingpreviously computed channel estimates 418.

A demapper 424 may input an equalized data stream 422 and may performthe inverse of the symbol mapping operation that was performed by themapper 306 from FIG. 3 thereby outputting a data stream 426. Ideally,this data stream 426 corresponds to the data 304 that was provided asinput to the transmitter 302, as illustrated in FIG. 3.

Association of Device with Network Controller

Certain aspects of the present disclosure support an efficientassociation of an apparatus in a piconet (e.g., a device of the Piconet100) with another apparatus, e.g., the piconet controller (PNC) 1E fromFIG. 1. FIG. 5 illustrates a sample association procedure, and FIG. 6illustrates example operations 600 for associating a second apparatus(e.g., a device of a piconet) with a first apparatus (e.g., a PNC of thesame piconet) in accordance with certain aspects of the presentdisclosure.

At 602, the first apparatus may transmit quasi-omni beacons 502 in aplurality of transmit directions 504 of the first apparatus. At 604, thesecond apparatus may receive the quasi-omni beacons 502, and maydetermine a preferred transmit direction of the first apparatus. At 606,the second apparatus may send Association Request Command (CMD) framesin any of association sub-contention access periods (S-CAPs) 506 usingone of transmit omni-directions of the second apparatus. EachAssociation Request may be sent with an Immediate Acknowledgement (IACK)mode. The Association Request may also include information about apreferred receive quasi-omni direction of the second apparatus.

At 608, the first apparatus may receive the previously transmittedAssociation Request CMD frames, and may respond, at 612, with an IACKmessage to a first Association Request detected in the association S-CAP506 using the preferred receive quasi-omni direction of the secondapparatus. If the second apparatus does not receive the IACK, then thesecond apparatus may resend, at 610, Association Request CMD framesusing another transmit omni-direction of the second apparatus. Thesecond apparatus may also apply back-off after each Association Requestin the association S-CAP 506.

Once a management entity (DME) provides Association Response informationto the first apparatus, the first apparatus may include a secondapparatus' Association Response Indication in quasi-omni beacontransmitted to the second apparatus, and may allocate, at 614, anassociation channel time allocation (CTA) for the second apparatus tocomplete association with the first apparatus. At 616, the firstapparatus may send an Association Response message in the allocatedassociation CTA. The Association Response may include information abouta preferred receive quasi-omni direction of the first apparatus.

At 618, the second apparatus may receive the Association Response, andmay send another Association Request CMD frame in a preferred directionAssociation S-CAP. At 620, the first apparatus may receive the otherAssociation Request CMD frame, and may allocate a channel timeallocation period (CTAP) 512 for beam training and for datatransmission. A regular contention access period (CAP) 510 may be usedfor a directional communication between peers (i.e., between devices ofthe piconet), and the CTAP 512 may be utilized for directionalcommunication between the first apparatus (e.g., the PNC) and the secondapparatus (e.g., the device), as illustrated in FIG. 5. It should bealso noted that the second apparatus may send an announce CMD to thefirst apparatus over one association S-CAP, and the first apparatus mayalways allocate the CTA to communicate with the second apparatus.

FIG. 7 illustrates an example of association flow in accordance withcertain aspects of the present disclosure. A DME 708 may send aMLME-ASSOCIATE.request (MLME: Media Access Control Sub-layer ManagementEntity) message 710 to a device (DEV) 706 to initiate DEV's associationwith a PNC 704. The DEV 706 may then transmit an Association Request CMDframe 712 to the PNC 704. The Association Request CMD frame 712, sent ina regular S-CAP, may comprise an identification of the DEV (i.e.,DEVID), as illustrated in FIG. 7. When the Association Request CMD frame712 is detected, the PNC 704 may respond to the DEV with an IACK message714. After that, the PNC 704 may send to the DEV 706 an AssociateResponse CMD frame 716 to allocate an association CTA for the DEV tocomplete association with the PNC. The Associate Response CMD frame 716may comprise DEV's ID and DEV's address, as illustrated in FIG. 7.

Before a time-out period 718 elapses, the DEV 706 may send to the PNC704 a second Association Request CMD frame 724 with DEV's address. Inthe meantime, the PNC 704 may indicate to a DME 702 association with theDEV 706 by sending a MLME-ASSOCIATE.indicate message 720, and the DEV706 may confirm association with the PNC 704 by sending aMLME-ASSOCIATE.confirm message 722 to the DME 708. TheMLME-ASSOCIATE.confirm message 722 may comprise DEV's address and DEV'sID, as illustrated in FIG. 7.

The PNC 704 may respond to the detected Association Request CMD frame724 with an IACK message 726, and may allocate a channel time allocationperiod (CTAP) for beam training and data transmission. The PNC maytransmit a beacon 728 to the DEV over the allocated CTAP, and the DEVmay send to the DME 708 a MLME-DEV-INFO.ind massage 730 indicating aDEV's information set. An optional SYNC frame 732 may be alsotransmitted from the DEV to the PNC. The sequence of messages 728-732may be repeated for every super-frame, as illustrated in FIG. 7.

FIG. 8 illustrates another example of association flow in accordancewith certain aspects of the present disclosure. A DME 808 may send aMLME-ASSOCIATE.request message 810 to a DEV 806 to initiate DEV'sassociation with a PNC 804. As illustrated in FIG. 8, AssociationRequest CMD frames 812 and 814 may be sent from the DEV 806 to the PNC804, but the PNC may not be able to detect these frames. Upon detectionat the PNC 804 of an Association Request CMD frame 816 that comprisesDEV's ID, the PNC may respond to the DEV with an IACK message 818. Alltransmissions 812-818 may be performed over an association S-CAP, asillustrated in FIG. 8.

The PNC may allocate an association CTA for the DEV 806 to complete theDEV's association by transmitting a beacon 820. The PNC may includeDEV's ID and DEV's address into an Associate Response CMD frame 822 sentto the DEV over the allocated association CTA. Upon detection of thisframe, the DEV 806 may respond to the PNC with an IACK message 824 alsotransmitted over the allocated association CTA.

Following the IACK message 824, the PNC 804 may indicate to a DME 802association with the DEV by sending a MLME-ASSOCIATE.indicate message826, and the DEV 806 may confirm the association with the PNC by sendinga MLME-ASSOCIATE.confirm message 828 to the DME 808. TheMLME-ASSOCIATE.confirm message 828 may comprise the DEV's address andDEV's ID, as illustrated in FIG. 8. Then, the DEV 806 may send to thePNC 804 a second Association Request CMD frame 830 with the DEV'saddress. The PNC 804 may respond to the detected Association Request CMDframe 830 with an IACK message 832, and then the PNC may allocate theCTAP for beam training and for data transmission. The transmissions 830and 832 may be performed over a preferred direction association S-CAP.

The PNC may transmit a beacon 834 to the DEV over the allocated CTAP,and the DEV may send to the DME 808 a MLME-DEV-INFO.ind massage 836indicating an information set of the DEV. An optional SYNC frame 838 maybe also transmitted from the DEV to the PNC. The sequence of messages834-838 may be repeated for every super-frame, as illustrated in FIG. 8.

Medium Allocation for Devices in the Network

One example of a media access control (MAC) is the use of a synchronizedsystem where all devices (DEVs) within a single network (such as apiconet or a basic service set (BSS) network) may be synchronized to acommon clock. A synchronization frame may be sent in every super-frameand may contain necessary information for time synchronization of DEVsin the network. Each DEV in the network may use a time stamp in thesynchronization frame to reset its super-frame clock to zero at thebeginning of the super-frame.

If a network controller (i.e., a piconet controller (PNC) or an accesspoint (AP)) is responsible to allocate a medium for devices in thenetwork, then the network controller may request the medium usingvarious methods of command frame transmission in defined time slotswithin the super-frame (i.e., beacon period). Such allocation may be afixed reservation, such as a channel time allocation (CTA) for the IEEE802.15.3c standard, or a distributed reservation protocol (DRP) for theEuropean Computer Manufacturer's Association (ECMA) standard. Allocationof the medium may be also semi-flexible where multiple devices maycompete over the medium, while directional transmission may not beallowed (i.e., restricted to low rate omni-directional traffic) or maybe predefined (i.e., a sectored or a directional CAP).

Channel time allocations (CTAs) may provide the best Quality of Service(QoS) for connections in the IEEE 802.15.3c system, but potentially CTAsmay also cause coexistence problems due to hidden nodes and the presenceof other networks such as the IEEE 802.11ad network. This may be becauseonce a DEV owns a CTA, then the DEV may perform transmission withoutusing a listen-before-talk mechanism. Therefore, in an environment wheremultiple physical layer (PHY) modes co-exist, the self-healingcontention access mechanism may provide improved channel utilization.However, due to the directional nature of the millimeter-wavetransmission supported by the IEEE 802.15.3c standard, new rules need tobe introduced to allow for directional communication in the CAP.

Certain aspects of the present disclosure relate to a method forallowing a directional ad-hoc peer-to-peer communication within thenetwork 100 illustrated in FIG. 1 without any involvement of a networkcoordinator (such as the PNC 1E or any access point) for medium accessallocation. The peer-to-peer communication may also supportantenna-pattern training and beamforming (i.e., pro-active beamforming).

Procedures for Accessing the Medium in Contention Access Period

A basic medium access mechanism during a CAP may be based on acarrier-sense multiple access with collision avoidance (CSMA/CA)approach. In order to minimize collisions, a transmitting DEV may berequired to first sense that a medium is idle for a random length oftime. The MAC may use clear channel assessment (CCA) capabilities of aPHY to detect whether the channel is busy or idle.

If there is insufficient time remaining in the CAP for the entire frameexchange sequence, then the transmitting DEV may not commencetransmission of the frame. The IEEE 802.15.3c DEV may be allowed totransmit one frame at a time with a back-off being applied to everyframe that is attempted during the CAP, except for an immediateacknowledgement (Imm-ACK) frame. The IEEE 802.11 DEV may be allowed totransmit one or more frames for the duration of a transmit opportunityperiod with the back-off being applied to every attempt for obtainingownership of the medium.

FIG. 9 illustrates operations 900 for ad-hoc directional transmission ina CAP with optional training of antenna-patterns (i.e., beamforming) inaccordance with certain aspects of the present disclosure. FIG. 10illustrates an example scenario for the ad-hoc directional transmissionin the CAP with no antenna-pattern training.

At 905, the DEV-1 may monitor a medium in the CAP, such as the CAP 1000illustrated in FIG. 10, for availability of the medium for datatransmission by the DEV-1. Also, at 910, the DEV-2 may monitor themedium in the CAP for availability of the medium for data transmissionby the DEV-2. At 915, after determining the medium is available for datatransmission, the DEV-1 may obtain the medium by transmitting an emptycommon mode signaling (CMS) frame 1002 in the CAP. At 920, the DEV-2 mayreceive the empty CMS frame transmitted by the DEV-1 indicating accessto the medium for data communication by the DEV-1 in the CAP. The emptyCMS frame 1002 may contain only a long preamble and one or more headers,and may be transmitted omni-directionally or quasi omni-directionally.

At 925 and 930, the DEV-1 and the DEV-2 may optionally performantenna-pattern training (i.e., beamforming) with each other in order todetermine preferred transmit and receive antenna patterns (i.e., sectoror beam patterns) of the DEV-1 and the DEV-2. Following the empty CMSframe and optional antenna-pattern training (i.e., beamforming), theDEV-1 may be allowed (after a minimum inter-frame space (MIFS) 1004) tosend, at 935, the data frame 1006 in any modulation coding scheme (MCS)supported by the CAP PHY mode using a known preferred transmit antennapattern. A DEV of the IEEE 802.11ad system may be allowed to send one ormore data frames in any MCS supported by the CAP PHY mode for aremaining duration of a transmit opportunity period. At 940, the DEV-2may receive the data frame 1006 transmitted in the CAP from the DEV-1.After a short inter-frame space (SIFS) 1008, the DEV-1 may receive anacknowledgement frame 1010 transmitted from the DEV-2, which confirmssuccessful reception of the data frame 1006 at the DEV-2.

It may be assumed that the preferred transmit pattern of the DEV-1 isknown as a result of previously performed beamforming. Therefore, theDEV-1 may use the preferred transmit pattern (i.e., sector or beam)toward the DEV-2 for transmitting the data frame 1006, at 935.

In order to allow for better efficiency in the CAP specified by the IEEE802.15.3c standard and since the back-off is being applied to everyframe attempted during the CAP, it may be desirable to allow forstandard aggregation of data frames within the CAP.

As illustrated in FIG. 9, the DEV-1 may optionally train the DEV-2 usinga beamforming protocol with at least one level of antenna-patterntraining. For certain aspects of the present disclosure, if the DEV-1failed to obtain the preferred transmit pattern, then the DEV-1 may notcommence transmission and may apply back-off before attempting tore-gain the medium.

For standards which allow bi-directional traffic within the transmitopportunity period and for standards which allow transmission ofmultiple data frames within the transmit opportunity period, theproposed medium access procedure in the CAP may be expanded to include asingle CMS frame and an optional training sequence per DEV per transmitopportunity period. The CMS frame may be also a vanguard CMS frame,which may be transmitted from the DEV when the medium for datatransmission in the CAP is obtained for the first time. The vanguard CMSframe may be employed for training of antenna patterns used for futurecommunication.

FIG. 11 illustrates example operations 1100 for antenna-patterntraining, which may be included as steps 925 and 930 in operations 900for the ad-hoc directional transmission illustrated in FIG. 9. FIG. 12illustrates an example scenario for the ad-hoc directional transmissionin the CAP with antenna-pattern training (i.e., beamforming) between twocommunicating devices. At 1110, the DEV-1 may perform beamforming withthe DEV-2 by sending training sequences 1206 using at least one transmitantenna pattern. Before sending the training sequences, the DEV-1 mayset a beam tracking bit in a PHY header of the transmitted empty CMSframe 1202 to ‘1’ in order to request beamforming with the other DEV(i.e., the DEV-2 illustrated in FIG. 12).

At 1120, the DEV-2 may receive the training sequences 1206 transmittedfrom the DEV-1 using a plurality of receive antenna patterns. The DEV-2may determine at least one preferred receive antenna pattern of theDEV-2 and at least one preferred transmit antenna pattern of the DEV-1.Following a short inter-frame space 1208, the DEV-2 may send a CMS frame1210 in order to access the medium in the CAP.

At 1130, following a minimum inter-frame space (MIFS) 1212, the DEV-2may send to the DEV-1 feedback information 1214 about a first preferredtransmit antenna pattern of the DEV-1 chosen from the at least onepreferred transmit antenna pattern of the DEV-1. The feedbackinformation 1214 may be transmitted using all available transmit antennadirections of the DEV-2. Optionally, the DEV-2 may send to the DEV-1feedback information 1218 about a second preferred transmit pattern ofthe DEV-1. The DEV-1 may sweep its receive antenna patterns duringreception of the feedback information 1214 transmitted from the DEV-2.

At 1140, following a SIFS 1220, the DEV-1 may determine at least onepreferred receive antenna pattern of the DEV-1 and at least onepreferred transmit antenna pattern of the DEV-2, and may send feedbackinformation 1222 to the DEV-2 about the at least one preferred transmitantenna pattern of the DEV-2. After a MIFS 1224, the DEV-1 may send adata frame 1226 using the first preferred transmit antenna pattern ofthe DEV-1 in any MCS supported by the CAP PHY mode. The transmitted dataframe 1226 may be received at the DEV-2 using a preferred receiveantenna pattern chosen from the at least one preferred receive antennapattern of the DEV-2. Following a SIFS 1228, the DEV-2 may send back tothe DEV-1 an acknowledgement frame 1230 using a preferred transmitantenna pattern chosen from the at least one preferred transmit antennapattern.

In a Symmetric Antenna System (SAS), there may be no need for sendingfeedback information during training of antenna directions. Therefore,each DEV in the SAS may train its peers by sending only repetitions oftraining sequence in every antenna direction. In the above descriptionof antenna-pattern training, each DEV (i.e., the DEV-1 and the DEV-2)may send a training sequence following an empty CMS frame, and each DEVmay then transmit data frames in a transmit antenna direction that maybe previously determined to be a preferred receive antenna direction.

CMS Frame Format and Channel Sensing

Each device in the IEEE 802.15.3c system may be required to send anempty CMS frame when trying to obtain medium access for transmittingdata in a PHY mode other than CMS. The empty CMS frame may betransmitted either omni-directionally or quasi omni-directionally. Asillustrated in FIG. 13, the empty CMS frame 1300 may comprise a Longpreamble 1302, a PHY header 1304, a MAC header 1306, a header check sum(HCS) 1308, and parity bits 1310.

FIG. 14 illustrates a structure of the PHY header 1304 from the CMSframe 1300 in accordance with certain aspects of the present disclosure.The PHY header 1304 may comprise: a scrambler seed identifier (ID) field1402, an aggregation bit 1404, an unequal error protection (UEP) bit1406, a modulation coding scheme (MCS) field 1408, a frame length field1410, a preamble type field 1412, a beam tracking bit 1414, a lowlatency mode bit 1416, a pilot word length bit 1418, a periodic channelestimation sequence (PCES) bit 1420, and a reserved field 1422.

All fields of the PHY header 1304 of the empty CMS frame 1300 may befixed, except the beam tracking bit 1414. The beam tracking bit 1414 maybe set to ‘1’ if training sequences for beam tracking follow the currentCMS frame 1300, and may be set to zero otherwise. The frame length field1410 may be an unsigned integer that indicates the number of octets ofthe MAC frame body excluding a frame check sequence (FCS) field. Theframe length field 1410 may be set to zero in the empty CMS frame 1300or may indicate duration of following one or more data frames.

The aggregation bit 1404 of the PHY header 1304 may be set to zero, andthe UEP bit 1406 may be also set to zero. The MCS field 1408 may be setto 0b00000. The preamble type field 1412 may be set to 0b00. The lowlatency mode bit 1416 may be set to zero, the pilot word length bit 1418may be set to zero, and the PCES bit 1420 may be set to zero.

FIG. 15 illustrates a structure of the MAC header 1306 of the empty CMSframe 1300 illustrated in FIG. 13 in accordance with certain aspects ofthe present disclosure. The MAC header 1306 may comprise: a framecontrol field 1502, a piconet identification (PNID) field 1504, adestination ID (DestID) field 1506, a source ID field (SrcID) field1508, a fragmentation control field 1510, and a stream index field 1512.

A DEV that listens to the medium may obtain peer information (i.e., thesource ID, the destination ID and the stream index) from the MAC headerpreviously transmitted from another DEV. Based on the information fromthe MAC header, the listening DEV may decide either to keep its receiveropen for one or more optional training sequences and/or a following dataframe, or to switch to a listening mode since a transmitting DEV may notbe any of its peers and/or the listening DEV may not be the transmissiondestination.

In order to allow better efficiency in the CAP and since the back-offmay be applied to every frame attempted during the CAP, certain aspectsof the present disclosure support utilization of unidirectional standardaggregation data frames in the CAP. Certain aspects of the presentdisclosure support removing restriction of an ACK policy to an 1 mm-ACKframe and to a No-ACK (i.e., negative acknowledgement) frame, and alsoallow for a block ACK frame.

The IEEE 802.15.3 piconet networks may use the carrier-sense multipleaccess with collision avoidance (CSMA/CA) scheme during the CAP and timedivision multiple access (TDMA) during a channel time allocation period(CTAP). The CAP may provide efficient method of coexistence with othernetworks, including the IEEE 802.11 networks, since the CSMA/CAalgorithm used in the CAP may be similar to the CSMA/CA algorithm usedin the IEEE 802.11 networks, i.e. a transmitter may use alisten-before-talk mechanism.

A clear channel assessment (CCA) mechanism in the CAP of the currentIEEE 802.15.3 system may not be robust enough to support directionaltransmission, which may lead to a considerable waste of power and poorco-existence. Certain aspects of the present disclosure support amodified CCA mechanism that may allow directional transmission in theCAP.

The PHY of the IEEE 802.15.3 system may require energy detection as apart of the CCA process. A sufficiently strong signal may result in aDEV signaling which may indicate that the medium is busy. This mayimprove the coexistence performance. The omni-directional (or quasiomni-directional) empty CMS frame may be used during the first part ofthe CCA (i.e., during listening for the Long preamble).

A start of a valid Long preamble sequence at a receive level equal to orgreater than a defined minimum sensitivity may indicate that the mediumis busy with a probability greater than 90% within 5 μs. The receiverCCA function may report in all circumstances that the medium is busywith any signal that may be 20 dB above the defined minimum sensitivityfor the CMS frame.

If a DEV wishing to initiate transfer detects the Long preamble duringits listen-before-talk period (i.e., during a back-off inter-framespace), the DEV may refrain from transmitting and may suspend itsback-off counter according to a back-off algorithm. This DEV may alsoremain in a receive mode during the CMS frame in order to obtain peerinformation from the MAC header. Based on the obtained peer information,the DEV may decide whether to keep its receiver open for one or moreoptional training sequences and/or following data frame, or to switch tothe listening mode if a transmitting device is not any of DEV's peersand/or DEV is not the transmission destination.

In order to obtain frame duration, the listening DEV may also decide todecode the optional training sequences and the PHY header of thefollowing data frame, even if the listening DEV may not be thetransmission destination. The listening DEV may then operate in a sleepmode for the duration of the data frame including an ACK frame in orderto save power consumption.

There is no mechanism in the current IEEE 802.15.3c standard, such as aNetwork Allocation Vector (NAV), to indicate transmission duration inthe CAP, i.e., to inform the listening DEV of a medium busy duration.This may lead to considerable waste of power and poor co-existence.Certain aspects of the present disclosure support adding durationindication to the CAP transmission. In one aspect, the fragmentationcontrol field 1510 of the MAC header 1306 of the empty CMS frame 1300illustrated in FIG. 15 may be reallocated to indicate durationinformation.

FIG. 16 illustrates a structure of the fragmentation control field 1510of the MAC header 1306 in accordance with certain aspects of the presentdisclosure. The fragmentation control field 1510 may comprise a durationfield 1602, a duration indication bit 1604, and a reserved field 1606.The Duration Indication (DI) bit 1604 may be set to ‘1’ to indicate thatbits 0-12 (i.e., the duration field 1602) may contain durationinformation. The duration field 1602 may contain the time inmicroseconds for which the medium is busy. A maximum allocated durationmay be 8 ms, which may allow for aggregated data frame of 256 KB, whilestill maintaining 8% frame error rate (FER) in a highest supported MCS.

Certain aspects of the present disclosure support a requirement that aDEV obtaining the medium for transmitting a data frame in the PHY modeother than CMS may transmit an omni-directional (or quasiomni-directional) CMS command frame before the data frame. Thisparticular command frame may include a new duration information element(IE) in a frame payload.

FIG. 17 illustrates a structure of the new duration IE field 1700 of theCMS command frame in accordance with certain aspects of the presentdisclosure. The duration IE field 1700 may comprise an element ID field1702, a length field 1704, and a duration field 1706. The duration field1706 may contains a time in microseconds for which the medium is busy. Amaximum allocated duration may be 8 ms, which may allow for aggregateddata frame of 256 KB, while still maintaining 8% frame error rate (FER)in a highest MCS.

FIG. 18 illustrates an example of durations 1800 and 1800′ indicatinghow long the medium may be busy for an ad-hoc directional transmissionwith no training in accordance with certain aspects of the presentdisclosure. For example, the duration 1800 may comprise a cumulativeduration of an empty CMS frame 1802, a MIFS 1804, a data frame 1806, aSIFS 1808, and an ACK frame 1810. The duration 1800 may be indicated inthe empty CMS frame 1802, while the duration 1800′ may be indicated inan empty CMS frame 1802′.

FIG. 19 illustrates an example of durations 1900 a and 1900 b indicatinghow long the medium may be busy for an ad-hoc directional transmissionwith training in accordance with certain aspects of the presentdisclosure. The duration 1900 a may be indicated within an empty CMSframe 1902, while the duration 1900 b may be indicated within an emptyCMS frame 1910. As illustrated in FIG. 19, the duration period 1900 amay comprise a cumulative duration of the empty CMS frame 1902, a MIFS1904, training sequences 1906, a SIFS 1908, the empty CMS frame 1910, aMIFS 1912, a first feedback information 1914, a MIFS 1916, a secondfeedback information 1918, a SIFS 1920, a feedback information 1922, aSIFS 1924, a data frame 1926, a SIFS 1928, and an ACK frame 1930. Asillustrated in FIG. 19, the duration period 1900 b may comprise acumulative duration of the empty CMS frame 1910, the MIFS 1912, thefirst feedback information 1914, the MIFS 1916, the second feedbackinformation 1918, the SIFS 1920, the feedback information 1922, the SIFS1924, the data frame 1926, the SIFS 1928, and the ACK frame 1930.

Transmission Opportunity and Slotted Access

As previously described, the newly proposed access methods may beapplied to any contention access protocol, including the IEEE 802.11 andthe enhanced distributed channel access (EDCA). This is because thesuggested mechanism may define a method for device listening to a mediumaccording to any medium access priority and timing rules in order toobtain and maintain a transmission direction from a vanguard CMS frameheaders according to new rules of ad-hoc (i.e. a proactive) beamforming.

This mechanism may be also applied for directional data transfer duringa contention-free period (CFP). In this case, a point coordinator (PC)may establish the CFP using a beacon frame. For millimeter-wave PHY,this beacon frame may be transferred using a CMS frame format, and maycomply with the previously described rules for ad-hoc (i.e., pro-active)beamforming.

Any data transfer within the CFP may be also performed according to thepreviously described rules of obtaining and maintaining transmissiondirection, from a vanguard CMS frame header and optional trainingsequence in a first transmission from each DEV.

Quasi-Omni Transmission and Reception

A DEV, which may be incapable of transmitting an omni-directional CMSframe and its preferred transmit pattern is unknown, may send the CMSframe in one of its supported transmit directions each time the DEVgains control over the medium.

If the DEV (i.e., the DEV-1) is capable of performing beamforming withanother DEV (i.e. a DEV-2), the DEV-1 may set a beam tracking field in aPHY header of the CMS frame to ‘1’. The DEV-1 may then train the DEV-2using the beamforming protocol with either one or two levels. In oneaspect of the present disclosure, the DEV-1 may use round-robin ofsupported transmit antenna directions each time the DEV-1 gains controlover the medium, while its preferred transmit pattern may be unknown.

A DEV, which may be incapable of transmitting an omni-directional CMSframe and its preferred transmit pattern is known, may use its preferredtransmit pattern (i.e., a sector or beam) each time the DEV gainscontrol over the medium.

FIG. 20 illustrates an example of quasi-omni preamble reception inaccordance with certain aspects of the present disclosure. A CMS frame2000 may be a vanguard CMS frame, which may be transmitted from the DEVwhen the medium for data transmission in a CAP is obtained for the firsttime. As illustrated in FIG. 20, a listening device (i.e. DEV-1), whichmay be not omni-capable, may sweep receive directions every definedperiod of time (i.e., every CCA detection time period) until thelistening device detects the presence of the preamble. The CCA detectiontime period may be 2 μs for a single carrier/high speed interface(SC/HIS) PHY and 9 μs for an audio-video (AV) PHY.

The sweep may be performed over all receive antenna directions of theDEV-1 or over a set of receive antenna directions suitable for receptionfrom its current peers. Upon detection of a Long preamble 2002 of theCMS frame 2000, the DEV-1 may find a working antenna direction for aparticular peer. The DEV-1 may use this working antenna direction untildetecting the PHY header 2004. The DEV-1 may detect the PHY header 2004,and then may proceed according the previously defined rules.

Accessing the Medium in Cap Using Long Preamble

Certain aspects of the present disclosure support utilizing a longpreamble for accessing the medium in a contention access period (CAP).FIG. 21 illustrates a frame structure 2100 with a long preamble 2102 inaccordance with certain aspects of the present disclosure. The DEVtrying to access the medium in the CAP may send the long preamble 2102followed by 8-bit Duration field 2104. The long preamble 2102 may besent according to a single carrier (SC) transmission scheme using a baserate, and may be protected with a Hamming 12′8 code. If the medium isgranted, then the DEV may be allowed to send over the regular CAP usingits best direction a data packet 2108 along with a header 2106 in anymodulation-coding scheme (MCS) supported by the CAP PHY mode.

In certain aspects of the present disclosure, it may be preferable touse a HSI MCS0 (High Speed Interface Modulation Coding Scheme 0)/AV LRP(Audio/Video Low-Rate PHY) preamble sequence for regular CAPtransmission, supporting only HSI PHY/AV PHY respectively. Therefore,the long preamble 2102 may comprise the CMS/HIS MSC0/AV LRP preamblesequence. A start of the valid CMS/HIS MSC0/AV LRP preamble sequence ata receive level equal to or greater than a defined minimum sensitivityfor the CMS may indicate that the medium is busy with a certainprobability, for example, with the probability greater than 90% withinapproximately 5 μs. The receiver clear channel assessment (CCA) functionmay report in certain circumstances that the medium is busy with anysignal approximately 20 dB above the minimum sensitivity for the CMS/HISMCS0/AV LRP long preamble sequence.

If a DEV (e.g., DEV-1) wishing to initiate a transfer detects theCMS/HIS MCS0/AV LRP preamble sequence during its listen-before-talk(i.e., during its back-off inter-frame space) period, the DEV-1 mayrefrain from transmitting and may suspend its back-off counter accordingto the back-off algorithm. The DEV-1 may also remain in receive mode inorder to obtain information about the duration of the frame 2100. Afterobtaining the duration information, the DEV-1 may go to sleep mode forthe duration period equal to the frame transmission (includingacknowledgement) in order to save power consumption.

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software component(s)and/or module(s), including, but not limited to a circuit, anapplication specific integrate circuit (ASIC), or processor. Generally,where there are operations illustrated in Figures, those operations mayhave corresponding counterpart means-plus-function components withsimilar numbering. For example, blocks 602-620, 905-940 and 1110-1140,illustrated in FIGS. 6, 9 and 11 correspond to circuit blocks 602A-620A,905A-940A and 1110A-1140A illustrated in FIGS. 6A, 9A and 11A.

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “determining” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” may include resolving, selecting, choosing, establishingand the like.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover: a, b, c,a-b, a-c, b-c, and a-b-c.

The various operations of methods described above may be performed byany suitable means capable of performing the operations, such as varioushardware and/or software component(s), circuits, and/or module(s).Generally, any operations illustrated in the Figures may be performed bycorresponding functional means capable of performing the operations.

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array signal (FPGA) or other programmable logic device(PLD), discrete gate or transistor logic, discrete hardware componentsor any combination thereof designed to perform the functions describedherein. A general purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thepresent disclosure may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Asoftware module may reside in any form of storage medium that is knownin the art. Some examples of storage media that may be used includerandom access memory (RAM), read only memory (ROM), flash memory, EPROMmemory, EEPROM memory, registers, a hard disk, a removable disk, aCD-ROM and so forth. A software module may comprise a singleinstruction, or many instructions, and may be distributed over severaldifferent code segments, among different programs, and across multiplestorage media. A storage medium may be coupled to a processor such thatthe processor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor.

The methods disclosed herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

The functions described may be implemented in hardware, software,firmware or any combination thereof. If implemented in software, thefunctions may be stored as one or more instructions on acomputer-readable medium. A storage media may be any available mediathat can be accessed by a computer. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code in the form of instructions or datastructures and that can be accessed by a computer. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers.

Thus, certain aspects may comprise a computer program product forperforming the operations presented herein. For example, such a computerprogram product may comprise a computer readable medium havinginstructions stored (and/or encoded) thereon, the instructions beingexecutable by one or more processors to perform the operations describedherein. For certain aspects, the computer program product may includepackaging material.

Software or instructions may also be transmitted over a transmissionmedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition oftransmission medium.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a user terminal and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a userterminal and/or base station can obtain the various methods uponcoupling or providing the storage means to the device. Moreover, anyother suitable technique for providing the methods and techniquesdescribed herein to a device can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

The techniques provided herein may be utilized in a variety ofapplications. For certain aspects, the techniques presented herein maybe incorporated in an access point, an access terminal or other type ofwireless device with processing logic and elements to perform thetechniques provided herein.

The invention claimed is:
 1. A method for wireless communications,comprising: monitoring, by an apparatus, a medium in a contention accessperiod (CAP) for availability of the medium for data transmission by theapparatus; after determining the medium is available for datatransmission by the apparatus, obtaining the medium by transmitting,from the apparatus, a common mode signaling (CMS) frame in the CAP;transmitting, from the apparatus, at least one data frame to anotherapparatus in the CAP over a wireless channel of the medium afterobtaining the medium; and performing training with the other apparatusto identify one or more preferred antenna patterns to use fortransmissions over the wireless channel.
 2. The method of claim 1,wherein transmitting the at least one data frame in the CAP comprisestransmitting the at least one data frame using a preferred transmitantenna pattern.
 3. The method of claim 1, wherein the trainingcomprises: transmitting one or more training sequences from theapparatus to the other apparatus using a plurality of transmit antennapatterns; and receiving feedback information from the other apparatusregarding a preferred transmit antenna pattern selected from theplurality of transmit antenna patterns.
 4. The method of claim 3,wherein transmitting one or more training sequences to the otherapparatus comprises transmitting one or more training sequences usingthe plurality of transmit antenna patterns, wherein the transmit antennapattern selected for transmitting each training sequence is selected ina round robin manner.
 5. The method of claim 1, wherein the trainingcomprises: receiving, at the apparatus, one or more training sequencestransmitted from the other apparatus; determining a preferred receiveantenna pattern and at least one preferred transmit antenna pattern ofthe other apparatus based on the received one or more trainingsequences; and sending feedback information to the other apparatus aboutthe preferred transmit antenna pattern.
 6. The method of claim 5,further comprising: storing the preferred receive antenna pattern at theapparatus; and transmitting, from the apparatus using the storedpreferred receive antenna pattern, another CMS frame and at least onedata packet in the CAP over the wireless channel of the medium next timewhen the medium is available for data transmission.
 7. The method ofclaim 5, further comprising: receiving from the other apparatus at leastone data frame using the preferred receive antenna pattern.
 8. Themethod of claim 1, wherein the preferred antenna pattern compriseseither a sector direction or a beam direction.
 9. A method for wirelesscommunications, comprising: monitoring, by an apparatus, a medium in acontention access period (CAP) for availability of the medium for datatransmission by the apparatus; after determining the medium is availablefor data transmission by the apparatus, obtaining the medium bytransmitting, from the apparatus, a common mode signaling (CMS) frame inthe CAP; and transmitting, from the apparatus, at least one data frameto another apparatus in the CAP over a wireless channel of the mediumafter obtaining the medium, wherein transmitting the CMS framecomprises: transmitting an omni-directional CMS frame, if the apparatusis capable of omni-directional transmission; and otherwise, transmittinga directional CMS frame.
 10. The method of claim 9, further comprising:transmitting one or more training sequences from the apparatus followingthe directional CMS frame.
 11. The method of claim 9, whereintransmitting the directional CMS frame comprises: transmitting thedirectional CMS frame using a transmit antenna pattern that is differentthan a transmit antenna pattern used to transmit a directional CMS framewhen the apparatus previously obtained access to the medium, if apreferred transmit antenna pattern of the apparatus is unknown.
 12. Themethod of claim 1, wherein the CMS frame consists of a long preamble, aphysical layer (PHY) header, a media access control (MAC) header, or aheader check sum (HCS) field, or any combination thereof.
 13. The methodof claim 12, wherein a beam tracking bit of the PHY header indicateswhether or not at least one training sequence follows the CMS frame. 14.The method of claim 12, wherein the MAC header comprises informationusable by another apparatus to determine whether to receive thetransmitted data frame and at least one optional training sequence, orto switch to a listening mode.
 15. The method of claim 12, wherein afragmentation control field of the MAC header comprises informationindicating for how long the medium will be in use.
 16. The method ofclaim 1, further comprising: sweeping over a set of receive antennapatterns until a preamble of a CMS frame transmitted by the otherapparatus is detected; determining, as a preferred receive antennapattern from the set of receive antenna patterns, a receive antennapattern used to detect the CMS frame; and using the preferred receiveantenna pattern to detect a physical layer (PHY) header of the receivedCMS frame.
 17. The method of claim 16, wherein the preamble of the CMSframe transmitted by the other apparatus is considered as being detectedif an energy level of the preamble is equal to or greater than a definedvalue.
 18. The method of claim 1, further comprising: detecting a longpreamble of a CMS frame transmitted from the other apparatus; andrefraining from transmitting, if the long preamble is detected during alisten-before-talk period of the apparatus.
 19. The method of claim 18,further comprising: deciding, based on information in a media accesscontrol (MAC) header of the long preamble, either to receive a datapacket and at least one optional training sequence or to switch to alistening mode.
 20. The method of claim 18, further comprising:decoding, at the apparatus, at least one training sequence and aphysical layer (PHY) header of a data packet following the longpreamble; and switching to a sleep mode for at least a remainingduration of the data packet.
 21. The method of claim 1, wherein aduration information element from a body of the transmitted CMS framecomprises information indicating to the other apparatus for how long themedium will be in use.
 22. The method of claim 1, wherein transmittingthe at least one data frame comprises transmitting the at least one dataframe during an allocated transmit opportunity period.
 23. The method ofclaim 1, wherein the apparatus is associated with a Symmetric AntennaSystem (SAS), and the method further comprising: determining a preferredreceive antenna pattern of the apparatus based on training sequencesreceived using multiple receive antenna patterns; and determining apreferred transmit antenna pattern of the apparatus that is same as thepreferred receive antenna pattern.
 24. The method of claim 23, furthercomprising: transmitting from the apparatus associated with the SAS atleast one data frame in the CAP using the preferred transmit antennapattern.
 25. The method of claim 1, further comprising: detecting, atthe apparatus, a transmission duration of at least one data frametransmitted from another apparatus by decoding a duration indication ofa received CMS frame, wherein the duration indication is included in amedia access control (MAC) header of the received CMS frame or in aduration information element of a frame body of the received CMS frame.26. The method of claim 1, further comprising: detecting, at theapparatus, a transmission duration of at least one data frametransmitted from another apparatus by decoding a value of a physicallayer (PHY) header length field of a received data frame.
 27. The methodof claim 1, wherein: transmitting the CMS frame comprises transmitting avanguard CMS frame in a transmit opportunity period.
 28. The method ofclaim 27, further comprising: transmitting at least one trainingsequence from the apparatus during the transmit opportunity period. 29.The method of claim 1, wherein: transmitting the CMS frame comprisestransmitting a vanguard CMS frame in a transmit opportunity period; andthe method further comprising receiving at least one training sequenceduring the transmit opportunity period.
 30. The method of claim 1,wherein: transmitting the CMS frame comprises transmitting in a transmitopportunity period; and wherein the data transmission over the medium inthe CAP comprises transmission of multiple data frames within thetransmit opportunity period.
 31. The method of claim 29, furthercomprising: transmitting a training sequence from the apparatus duringthe transmit opportunity period.
 32. The method of claim 1, wherein:transmitting the CMS frame comprises transmitting in a transmitopportunity period; and wherein the data transmission over the medium inthe CAP comprises transmission in both directions between the apparatusand the another apparatus within the transmit opportunity period. 33.The method of claim 32, further comprising: transmitting a trainingsequence from the apparatus during the transmit opportunity period. 34.The method of claim 1, wherein the CMS frame transmitted over the CAPusing a single carrier (SC) scheme comprises a CMS long preamble and aduration field indicating duration of the CMS frame.
 35. The method ofclaim 34, wherein the at least one data frame following the CMS longpreamble and the duration field is transmitted over the wireless channelof the medium using a preferred transmit antenna direction of theapparatus.
 36. The method of claim 1, wherein the CMS frame transmittedover the CAP according to an Orthogonal Frequency Division MultiplexingHigh Speed Interface (OFDM HSI) scheme comprises a HSI Modulation CodingScheme 0 (HSI MCS0) long preamble sequence and a duration fieldindicating duration of the CMS frame.
 37. The method of claim 1, whereinthe CMS frame transmitted over the CAP according to an OrthogonalFrequency Division Multiplexing Audio/Video (OFDM AV) scheme comprisesan AV Low-Rate Physical Layer (AV LRP) long preamble sequence and aduration field indicating duration of the CMS frame.
 38. An apparatusfor wireless communications, comprising: a monitoring circuit configuredto monitor a medium in a contention access period (CAP) for availabilityof the medium for data transmission by the apparatus; a transmitterconfigured to obtain the medium by transmitting a common mode signaling(CMS) frame in the CAP, after determining the medium is available fordata transmission by the apparatus, and wherein the transmitter is alsoconfigured to transmit at least one data frame to another apparatus inthe CAP over a wireless channel of the medium after obtaining themedium; and a circuit configured to perform training with the otherapparatus to identify one or more preferred antenna patterns to use fortransmissions over the wireless channel.
 39. An apparatus for wirelesscommunications, comprising: a monitoring circuit configured to monitor amedium in a contention access period (CAP) for availability of themedium for data transmission by the apparatus; and a transmitterconfigured to obtain the medium by transmitting a common mode signaling(CMS) frame in the CAP, after determining the medium is available fordata transmission by the apparatus, and wherein the transmitter is alsoconfigured to: transmit at least one data frame to another apparatus inthe CAP over a wireless channel of the medium after obtaining themedium; transmit an omni-directional CMS frame, if the apparatus iscapable of omni-directional transmission; and otherwise, transmit adirectional CMS frame.
 40. The apparatus of claim 38, wherein the CMSframe consists of a long preamble, a physical layer (PHY) header, amedia access control (MAC) header, or a header check sum (HCS) field, orany combination thereof.
 41. The apparatus of claim 38, furthercomprising: a sweeping circuit configured to sweep over a set of receiveantenna patterns until a preamble of a CMS frame transmitted by theother apparatus is detected; a processor configured to determine, as apreferred receive antenna pattern from the set of receive antennapatterns, a receive antenna pattern used to detect the CMS frame; and adetector configured to use the preferred receive antenna pattern todetect a physical layer (PHY) header of the received CMS frame.
 42. Theapparatus of claim 38, wherein the apparatus is associated with aSymmetric Antenna System (SAS), and the apparatus further comprising: aprocessor configured to determine a preferred receive antenna pattern ofthe apparatus based on training sequences received using multiplereceive antenna patterns, and wherein the processor is also configuredto determine a preferred transmit antenna pattern of the apparatus thatis same as the preferred receive antenna pattern.
 43. The apparatus ofclaim 38, wherein: the transmitter is also configured to transmit avanguard CMS frame in a transmit opportunity period; and the apparatusfurther comprising a receiver configured to receive at least onetraining sequence during the transmit opportunity period.
 44. Theapparatus of claim 38, wherein the CMS frame transmitted over the CAPusing a single carrier (SC) scheme comprises a CMS long preamble and aduration field indicating duration of the CMS frame.
 45. The apparatusof claim 38, wherein the CMS frame transmitted over the CAP according toan Orthogonal Frequency Division Multiplexing High Speed Interface (OFDMHSI) scheme comprises a HSI Modulation Coding Scheme 0 (HSI MCS0) longpreamble sequence and a duration field indicating duration of the CMSframe.
 46. The apparatus of claim 38, wherein the CMS frame transmittedover the CAP according to an Orthogonal Frequency Division MultiplexingAudio/Video (OFDM AV) scheme comprises an AV Low-Rate Physical Layer (AVLRP) long preamble sequence and a duration field indicating duration ofthe CMS frame.
 47. An apparatus for wireless communications, comprising:means for monitoring a medium in a contention access period (CAP) foravailability of the medium for data transmission by the apparatus; meansfor obtaining the medium by transmitting, from the apparatus, a commonmode signaling (CMS) frame in the CAP, after determining the medium isavailable for data transmission by the apparatus; means for transmittingat least one data frame to another apparatus in the CAP over a wirelesschannel of the medium after obtaining the medium; and means forperforming training with the other apparatus to identify one or morepreferred antenna patterns to use for transmissions over the wirelesschannel.
 48. An apparatus for wireless communications, comprising: meansfor monitoring a medium in a contention access period (CAP) foravailability of the medium for data transmission by the apparatus; meansfor obtaining the medium by transmitting, from the apparatus, a commonmode signaling (CMS) frame in the CAP, after determining the medium isavailable for data transmission by the apparatus; and means fortransmitting at least one data frame to another apparatus in the CAPover a wireless channel of the medium after obtaining the medium,wherein the means for transmitting the CMS frame comprises: means fortransmitting an omni-directional CMS frame, if the apparatus is capableof omni-directional transmission; and otherwise, means for transmittinga directional CMS frame.
 49. The apparatus of claim 47, wherein the CMSframe consists of a long preamble, a physical layer (PHY) header, amedia access control (MAC) header, or a header check sum (HCS) field, orany combination thereof.
 50. The apparatus of claim 47, furthercomprising: means for sweeping over a set of receive antenna patternsuntil a preamble of a CMS frame transmitted by the other apparatus isdetected; means for determining, as a preferred receive antenna patternfrom the set of receive antenna patterns, a receive antenna pattern usedto detect the CMS frame; and means for using the preferred receiveantenna pattern to detect a physical layer (PHY) header of the receivedCMS frame.
 51. The apparatus of claim 47, wherein the apparatus isassociated with a Symmetric Antenna System (SAS), and the apparatusfurther comprising: means for determining a preferred receive antennapattern of the apparatus based on training sequences received usingmultiple receive antenna patterns; and means for determining a preferredtransmit antenna pattern of the apparatus that is same as the preferredreceive antenna pattern.
 52. The apparatus of claim 47, wherein: themeans for transmitting the CMS frame comprises means for transmitting avanguard CMS frame in a transmit opportunity period; and the apparatusfurther comprising means for receiving at least one training sequenceduring the transmit opportunity period.
 53. The apparatus of claim 47,wherein the CMS frame transmitted over the CAP using a single carrier(SC) scheme comprises a CMS long preamble and a duration fieldindicating duration of the CMS frame.
 54. The apparatus of claim 47,wherein the CMS frame transmitted over the CAP according to anOrthogonal Frequency Division Multiplexing High Speed Interface (OFDMHSI) scheme comprises a HSI Modulation Coding Scheme 0 (HSI MCS0) longpreamble sequence and a duration field indicating duration of the CMSframe.
 55. The apparatus of claim 47, wherein the CMS frame transmittedover the CAP according to an Orthogonal Frequency Division MultiplexingAudio/Video (OFDM AV) scheme comprises an AV Low-Rate Physical Layer (AVLRP) long preamble sequence and a duration field indicating duration ofthe CMS frame.
 56. A computer-program product for wirelesscommunications, comprising a non-transitory, tangible computer-readablestorage medium encoded with instructions executable to: monitor, by anapparatus, a medium in a contention access period (CAP) for availabilityof the medium for data transmission by the apparatus; obtain the mediumby transmitting, from the apparatus, a common mode signaling (CMS) framein the CAP, after determining the medium is available for datatransmission by the apparatus; transmit, from the apparatus, at leastone data frame to another apparatus in the CAP over a wireless channelof the medium after obtaining the medium; and perform training with theother apparatus to identify one or more preferred antenna patterns touse for transmissions over the wireless channel.
 57. A wireless node,comprising: at least one antenna; a monitoring circuit configured tomonitor a medium in a contention access period (CAP) for availability ofthe medium for data transmission by the wireless node; a transmitterconfigured to obtain the medium by transmitting via the at least oneantenna a common mode signaling (CMS) frame in the CAP, afterdetermining the medium is available for data transmission by thewireless node, and wherein the transmitter is also configured totransmit via the at least one antenna at least one data frame to anotherwireless node in the CAP over a wireless channel of the medium afterobtaining the medium; and a circuit configured to perform training withthe other wireless node to identify one or more preferred antennapatterns to use for transmissions over the wireless channel.
 58. Amethod for wireless communications, comprising: receiving, by anapparatus, a common mode signaling (CMS) frame transmitted by anotherapparatus indicating access to a medium for data communication by theother apparatus in a contention access period (CAP); receiving, from theother apparatus once the access to the medium for data communication isindicated at the apparatus, at least one data frame over a wirelesschannel of the medium in the CAP; and transmitting, to the otherapparatus, an acknowledgement that the at least one data frame issuccessfully received over the wireless channel of the medium in theCAP, wherein receiving the at least one data frame comprises receivingthe at least one data frame using a preferred receive antenna pattern.59. The method of claim 58, wherein the CMS frame transmitted by theother apparatus is an omni-directional CMS frame.
 60. The method ofclaim 58, wherein the preferred receive antenna pattern is determined byperforming training with the other apparatus.
 61. A method for wirelesscommunications, comprising: receiving, by an apparatus, a common modesignaling (CMS) frame transmitted by another apparatus indicating accessto a medium for data communication by the other apparatus in acontention access period (CAP); receiving, from the other apparatus oncethe access to the medium for data communication is indicated at theapparatus, at least one data frame over a wireless channel of the mediumin the CAP; and transmitting, to the other apparatus, an acknowledgementthat the at least one data frame is successfully received over thewireless channel of the medium in the CAP, wherein the received CMSframe is a vanguard CMS frame, and the method further comprising:sweeping over a set of receive antenna patterns for multiple definedperiods of time until a long preamble of the vanguard CMS frame isdetected; determining, as a preferred receive antenna pattern, a receiveantenna pattern from the set of receive antenna patterns used to detectthe long preamble; and using the preferred receive antenna pattern todetect a physical layer (PHY) header of the vanguard CMS frame.
 62. Themethod of claim 58, further comprising: detecting, at the apparatus, along preamble of another CMS frame; and refraining from transmitting ifthe long preamble is detected during a listen-before-talk period of theapparatus.
 63. The method of claim 62, further comprising: receiving, atthe apparatus, a media access control (MAC) header of the other CMSframe; and deciding, based on information in the MAC header, whether toreceive a data packet and at least one optional training sequence or toswitch to a listening mode.
 64. The method of claim 62, furthercomprising: decoding, at the apparatus, at least one training sequenceand a physical layer (PHY) header of a data packet following the longpreamble; and switching to a sleep mode for at least a remainingduration of the data packet.
 65. The method of claim 58, furthercomprising: enabling an ad-hoc directional communication over the mediumin the CAP.
 66. The method of claim 65, wherein the ad-hoc directionalcommunication is enabled without any communication with a networkcoordinator.
 67. The method of claim 66, further comprising: storing thepreferred receive antenna pattern at the apparatus; and receiving, atthe apparatus using the stored preferred receive antenna pattern,another CMS frame and at least one data packet transmitted from theother apparatus over the wireless channel of the medium in the CAP. 68.The method of claim 58, wherein the received CMS frame comprises a longpreamble and a duration field indicating duration of the CMS frame. 69.The method of claim 68, wherein the long preamble comprises at least oneof: a CMS sequence, a High Speed Interface Modulation Coding Scheme 0(HSI MCS0) sequence or an Audio-Video Low-Rate Physical Layer (AV LRP)sequence.
 70. The method of claim 68, wherein receiving the CMS framecomprises: receiving at least a start of the long preamble, and whereinthe medium is in use if an energy level of the received start of thelong preamble is equal to or greater than a defined value.
 71. Themethod of claim 70, further comprising: reporting that the medium is inuse by utilizing the Clear Channel Assessment (CCA) function of theapparatus.
 72. The method of claim 70, further comprising: refrainingfrom transmitting if the start of the long preamble is received during alisten-before-talk period of the apparatus.
 73. The method of claim 72,further comprising: staying in a receive mode to obtain informationabout remaining duration of the CMS frame based on a value of theduration field; and switching to a sleep mode for the remaining durationof the CMS frame.
 74. An apparatus for wireless communications,comprising: a receiver configured to receive a common mode signaling(CMS) frame transmitted by another apparatus indicating access to amedium for data communication by the other apparatus in a contentionaccess period (CAP), wherein the receiver is also configured to receive,from the other apparatus once the access to the medium for datacommunication is indicated at the apparatus, at least one data frameover a wireless channel of the medium in the CAP; and a transmitterconfigured to transmit, to the other apparatus, an acknowledgement thatthe at least one data frame is successfully received over the wirelesschannel of the medium in the CAP, wherein the receiver is alsoconfigured to receive the at least one data frame using a preferredreceive antenna pattern.
 75. The apparatus of claim 74, wherein the CMSframe transmitted by the other apparatus is an omni-directional CMSframe.
 76. The apparatus of claim 74, wherein the preferred receiveantenna pattern is determined by performing training with the otherapparatus.
 77. An apparatus for wireless communications, comprising: areceiver configured to receive a common mode signaling (CMS) frametransmitted by another apparatus indicating access to a medium for datacommunication by the other apparatus in a contention access period(CAP), wherein the receiver is also configured to receive, from theother apparatus once the access to the medium for data communication isindicated at the apparatus, at least one data frame over a wirelesschannel of the medium in the CAP; and a transmitter configured totransmit, to the other apparatus, an acknowledgement that the at leastone data frame is successfully received over the wireless channel of themedium in the CAP, wherein the received CMS frame is a vanguard CMSframe, and the apparatus further comprising: a sweeping circuitconfigured to sweep over a set of receive antenna patterns for multipledefined periods of time until a long preamble of the vanguard CMS frameis detected; a processor configured to determine, as a preferred receiveantenna pattern, a receive antenna pattern from the set of receiveantenna patterns used to detect the long preamble; and a detectorconfigured to use the preferred receive antenna pattern to detect aphysical layer (PHY) header of the vanguard CMS frame.
 78. The apparatusof claim 74, further comprising: a detector configured to detect a longpreamble of another CMS frame; and a circuit configured to refrain fromtransmitting if the long preamble is detected during alisten-before-talk period of the apparatus.
 79. The apparatus of claim74, further comprising: a circuit configured to enable an ad-hocdirectional communication over the medium in the CAP.
 80. The apparatusof claim 74, wherein the received CMS frame comprises a long preambleand a duration field indicating duration of the CMS frame.
 81. Theapparatus of claim 80, wherein the receiver is also configured toreceive at least a start of the long preamble, and wherein the medium isin use if an energy level of the received start of the long preamble isequal to or greater than a defined value.
 82. The apparatus of claim 81,further comprising: a circuit configured to refrain from transmitting ifthe start of the long preamble is received during a listen-before-talkperiod of the apparatus.
 83. An apparatus for wireless communications,comprising: means for receiving a common mode signaling (CMS) frametransmitted by another apparatus indicating access to a medium for datacommunication by the other apparatus in a contention access period(CAP); means for receiving, from the other apparatus once the access tothe medium for data communication is indicated at the apparatus, atleast one data frame over a wireless channel of the medium in the CAP;and means for transmitting, to the other apparatus, an acknowledgementthat the at least one data frame is successfully received over thewireless channel of the medium in the CAP, wherein the means forreceiving the at least one data frame comprises means for receiving theat least one data frame using a preferred receive antenna pattern. 84.The apparatus of claim 83, wherein the CMS frame transmitted by theother apparatus is an omni-directional CMS frame.
 85. The apparatus ofclaim 83, wherein the preferred receive antenna pattern is determined byperforming training with the other apparatus.
 86. An apparatus forwireless communications, comprising: means for receiving a common modesignaling (CMS) frame transmitted by another apparatus indicating accessto a medium for data communication by the other apparatus in acontention access period (CAP); means for receiving, from the otherapparatus once the access to the medium for data communication isindicated at the apparatus, at least one data frame over a wirelesschannel of the medium in the CAP; and means for transmitting, to theother apparatus, an acknowledgement that the at least one data frame issuccessfully received over the wireless channel of the medium in theCAP, wherein the received CMS frame is a vanguard CMS frame, and theapparatus further comprising: means for sweeping over a set of receiveantenna patterns for multiple defined periods of time until a longpreamble of the vanguard CMS frame is detected; means for determining,as a preferred receive antenna pattern, a receive antenna pattern fromthe set of receive antenna patterns used to detect the long preamble;and means for using the preferred receive antenna pattern to detect aphysical layer (PHY) header of the vanguard CMS frame.
 87. The apparatusof claim 83, further comprising: means for detecting a long preamble ofanother CMS frame; and means for refraining from transmitting if thelong preamble is detected during a listen-before-talk period of theapparatus.
 88. The apparatus of claim 83, further comprising: means forenabling an ad-hoc directional communication over the medium in the CAP.89. The apparatus of claim 83, wherein the received CMS frame comprisesa long preamble and a duration field indicating duration of the CMSframe.
 90. The apparatus of claim 89, wherein the means for receivingthe CMS frame comprises: means for receiving at least a start of thelong preamble, and wherein the medium is in use if an energy level ofthe received start of the long preamble is equal to or greater than adefined value.
 91. The apparatus of claim 90, further comprising: meansfor refraining from transmitting if the start of the long preamble isreceived during a listen-before-talk period of the apparatus.
 92. Acomputer-program product for wireless communications, comprising anon-transitory, tangible computer-readable storage medium encoded withinstructions executable to: receive, by an apparatus, a common modesignaling (CMS) frame transmitted by another apparatus indicating accessto a medium for data communication by the other apparatus in acontention access period (CAP); receive, from the other apparatus oncethe access to the medium for data communication is indicated at theapparatus, at least one data frame over a wireless channel of the mediumin the CAP; and transmit, to the other apparatus, an acknowledgementthat the at least one data frame is successfully received over thewireless channel of the medium in the CAP, wherein receiving the atleast one data frame comprises receiving the at least one data frameusing a preferred receive antenna pattern.
 93. A wireless node,comprising: at least one antenna; a receiver configured to receive viathe at least one antenna a common mode signaling (CMS) frame transmittedby another wireless node indicating access to a medium for datacommunication by the other wireless node in a contention access period(CAP), wherein the receiver is also configured to receive via the atleast one antenna, from the other wireless node once the access to themedium for data communication is indicated at the wireless node, atleast one data frame over a wireless channel of the medium in the CAP;and a transmitter configured to transmit via the at least one antenna,to the other wireless node, an acknowledgement that the at least onedata frame is successfully received over the wireless channel of themedium in the CAP, wherein the receiver is also configured to receivethe at least one data frame using a preferred receive antenna pattern.